How many eggs do fleas lay?

Summary

An average female cat flea lays 20-30 eggs a day. At a maximum, one female was observed depositing 46.3 eggs a day. Fleas live for around a week on their acquired host. Thus, females lay 160-180 eggs during their normal lifespans.

Details

Reproductive Biology

Ovaries

Female fleas have two ovaries, each composed of six ovarioles. From these 12 ovarioles, an average of over 20 eggs are produced per day. Thus, some ovarioles produce multiple eggs a day.

Immature Egg Cells

During a female’s life, each ovariole can produce at least 50 oocytes (immature egg cells). In theory, it’s possible for a female to lay 400-900 eggs during her lifespan. A more recent study shows this estimate is low.

Mature Egg Cells

Reproducing females have mature egg cells in half of their ovarioles. On average, females contain six eggs within their abdomens Fig 1. They can only hold 6-7 eggs at time due to the relatively large size of flea eggs. However, in one instance, a female in peak production was observed to hold 13 mature eggs in her abdomen.

Fig 1 Number of female fleas (y-axis) with a certain number of eggs in their abdomens (x-axis). A total of 220 fleas were observed.

Rate of Egg Production

Average Egg Production

Cat fleas are highly reproductive. A single healthy female produces an average of 20-30 eggs per day, roughly one egg an hour Fig 2. Incredibly, 1.05 times a female flea’s body weight is produced in eggs every 24 hours.

Fig 2 Number of eggs produced per cat flea (y-axis) at every hour across a day (x-axis). The scotophase (dark cycle) occurred from 1800 to 0600 hours.

Initiation of Egg Laying

Egg production begins 1-2 days after a female flea takes her first blood meal. No eggs are produced on the first day of feeding. Oviposition rates start low, with 5-10 eggs laid per day on the second and third days of feeding.

Rising Rates & Tapering Off

The oviposition rate rapidly rises and peaks 4-9 days after the first blood meal (5-10 days after cocoon emergence) Fig 3. At peak production, a female is capable of producing up to 46.3 eggs a day. However, in most cases, females deposit a maximum of 25-30 eggs per day.

After peaking, a relatively high rate of egg production is sustained for 2-4 weeks before it gently tapers off.

Fig 3 Average number of eggs laid per day by individual female cat fleas (y-axis) for 14 days following their first blood meal (x-axis).

Reproductive Capacity

A female flea will continue laying eggs as long as she survives. However, the oviposition rate will progressively decrease with age. One study observed a 113 day old female producing 4-5 eggs a day. Reproductive capacity is believed to near depletion by the third month of continuous egg laying.

Flea Lifespan

Natural Conditions

In natural settings, adult fleas live for about a week. Their lifespan is drastically shortened due to host grooming. In one study, a flea’s average life expectancy was 7.8 days when living on a cat. Over the course of a week, cats groom off and ingest near 50% of the fleas placed on them. A cats kills 3-12 fleas a day.

Artificial Conditions

Adult cat fleas can live for well over 100 days. When host grooming was restricted, 58% of females and 50% of males survived on cats for 113 days. In an artificial environment, cat fleas lived for an average of 156 days, and a maximum of 185 days.

Flea Fecundity

Natural Conditions

The total number of eggs a female can produce depends upon her lifespan. Older studies state that average fecundity is about 800 eggs. Newer studies conclude that a female will lay less than 200 eggs during her normal lifetime. This lower number is coherent, given that the average female’s lifespan is 7 days, and she’ll produce 25 eggs a day (175 eggs total).

Artificial Conditions

Flea fecundity drastically increases when the host is restricted from grooming itself. A female flea will produce an average of 1348 eggs over 50 days. One female laid a maximum of 1745 eggs during this time. Well over 2000 eggs were produced by this female by day 113.

Factors Affecting Fecundity

Flea Allergies

Hosts afflicted with flea allergy dermatitis are more efficient at grooming. This results in more fleas getting killed from scratching, nipping, or ingestion. Allergic animals may also produce serum or tissue that negatively affects flea fecundity.

Large Flea Populations

Less eggs are laid when the host is densely populated with female fleas.

Non-Preferred Hosts

A decline in fecundity occurs if fleas don’t feed on their preferred host species. For example, when feeding exclusively on human blood, cat fleas only lay 1-4 eggs a day.

Single Mating

Females produce the largest number of viable eggs after they’ve mated with multiple males. They produce far fewer eggs if they only mate once.

Viable & Non-Viable Eggs

A large portion of the deposited eggs won’t hatch. Fertile eggs only account for 30-46% of the total eggs laid. The non-viable eggs serve as a food source for larvae. Flea larvae can’t develop into adults without this nutrient supplement.

References

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